(Reuters) - Virgin Money UK on Thursday warned of a higher cost-to-income ratio in the second half of the year as the British bank delayed certain restructuring plans due to the Nationwide deal.

The lender, which earlier this year agreed to a 2.9 billion pound all-cash takeover by building society Nationwide, reported an 18% rise in statutory pre-tax profit on ordinary activities to 279 million pounds ($356.56 million) for the six months ended March 31.

The cost-to-income ratio is a key measure of efficiency where lower is better.

($1 = 0.7825 pounds)

(Reporting by Echha Jain in Bengaluru; Editing by Subhranshu Sahu)